1. Field of the Invention
The present invention relates to a photographing apparatus and a photographing method, and more particularly, to a photographing apparatus and method that can maintain a desired number of photographed images per second or a desired frame rate while ensuring sufficient exposure of a subject.
2. Description of the Related Art
Some photographing apparatuses have a photographing mode that can allow the photographing apparatus to continuously photograph a plurality of images with a photographing operation. Hereinafter, the photographing mode for photographing a plurality of images continuously will be referred to as a continuous photographing mode. For example, a photographing apparatus may photograph a plurality of images per second by fixing a shutter speed for each photographed image.
In addition, some photographing apparatuses have a photographing mode, in which a moving picture can be taken by recording a plurality of images per second, when a shutter button is pushed. Hereinafter, the photographing mode for taking a moving picture will be referred to as a moving picture mode. A frame rate is the number of times per second that the output image is updated, and a unit of the frame rate is fps (frame per second). For example, a case where the images are displayed and updated 30 times per second has a frame rate of 30 fps.
However, the conventional photographing apparatus performing the continuous photographing mode and the moving picture mode has the following problems.
FIGS. 1(a) and 1(b) are conceptual diagrams illustrating an example of what occurs when a plurality of continuous images are photographed in the conventional photographing apparatus capable of performing the continuous photographing mode and the moving picture mode.
In order to increase the number of photographed images per second in the continuous photographing mode, or to increase the frame rate in the moving picture mode, an exposure time is reduced as shown in the high SS (shutter speed) example of FIG. 1(a). However, in order to photograph, for example, 10 images during a second, the shutter speed must be faster than 1/10 second in consideration of the time taken for inputting photographed image data. Therefore, when a subject is dark, for example, at night or indoors, sufficient image data typically cannot be obtained due to lack of exposure in the environment in which the subject is present.
In addition, if the shutter speed is lowered in order to ensure a sufficient exposure amount as shown in the low SS example of FIG. 1(b), the number of photographed images or the frame rate per second is reduced.
In order to solve the above problems, an exposure for a short period of time is taken repeatedly, and images obtained by the exposures are combined at predetermined intervals. Then, the desired shutter speed and the number of photographed images, or the frame rate, can be attained.
An example of a method for taking an exposure for a short period of time repeatedly and combining images obtained by the exposures is disclosed in Japanese Laid-open Patent No. 2003-319269. However, according to this method, an image having a plurality of periods of exposure times is combined, and thus, a plurality of images having the same exposure times are not photographed, or a moving picture having the same exposure times is not photographed. As described above, according to the conventional photographing apparatus, it is difficult to achieve a fast shutter speed and a high number of photographed images, or a high frame rate, simultaneously.